Businesses and other organizations are increasingly turning to internet protocol (IP)-based telecommunications services. IP is a packet-switched protocol, which allows for greater flexibility than previous circuit-switched technologies. IP is also a suitable base upon which to deploy additional multimedia telephony services beyond voice telephony, including video, presence, messaging, and so on. For example, IP Multimedia Subsystem (IMS) is a standardized next-generation networking architecture for telephony services that uses IP and the session initiation protocol (SIP). SIP is a signaling protocol used for controlling communications sessions over IP.